Current motor



(No Model.)

W. LANGDON-DAVIES.

ALTERNATING CURRENT MOTOR. No. 601,023. Patented Mar. 22,1898.

m JM a W UNITED STATES PATENT OFFICE.

\VALTER LANGDON-DAVIES, OF LONDON, ENGLAND, ASSIGNOR TO THE DAVIES MOTORCOMPANY, LIMITED, OF SAME PLACE.

ALTERNATlNG-CURRENT MOTOR.

SPECIFICATION forming part of Letters Patent No. 601,023, dated March22, 1898.

Application filed November 15, 1897. serial No. 658,591. (No model.)

To all whom, it may concern:

Be itknown that LWALTER LANGDON-DA- VIEs, a subject of the Queen ofGreat Britain, residing at 16 Red Lion street, Olerkenwell, London,England, have invented certain new and useful Improvements inAlternating'Ourrent Motors, of which the following is a specification.

In single-phase motors as now ordinarily constructed theenergizing-current passes, when the motor is running, through a singleset of coils, which may be in series. These are called therunning-coils. They have as low resistance as possible. Such a motorwill not start from rest. To start it, another set of coi1s,which mayalso be in series with each other,are used in addition to therunning-coils. These are called the starting-coils and are set at anangle to the running-coils. They are wound with fewer turns than therunning coils and a-resistance or condenser is added in series with themto reduce the lag (behind the volts) of the current flowing in them.They are then joined in parallel to the running-coils. The currenttherefore lags behind the volts less in the starting-coils than in therunning ones, and thus a rotating field is obtained by which the motoris started. A choking-coil is sometimes put in series with therunning-coils to increase their angle of lag. This methodof starting hasthis incon- Venience,that the running-coil is put straight onto themains when the machine is at rest, under which circumstances it takes alarge and wasteful amount of current, or it a choking-coil is addedthere is a loss of efficiency. This is a necessity if the running-coilsare properly Wound for running.

According to my invention I wind the running-coil as usual; but insteadof using it as before I add resistance to it when starting, and thusreduce the lag of the current through it behind the volts. The second orstarting coil I wind of a larger number of turns, so as to have a largeself-induction and as low a resistance as possible, so that the lag ofthe current behind the volts is large. The running-coil now lags lessthan the starting-coil and the rotating field is more economicallyobtained. WVhen the motor has attained sufficient speed to allow of itsbeing driven synchronously, current is cut off from the starting-coilsand the resistance cut out of the runrung-c011 clrcuit.

The figure shows in end view an example of the field-magnet ring of anelectric motor thus wound with starting and running coils and havingswitch connections shown diagrammatically for putting a resistance intothe circuit of the running-coils at the time of starting.

The field-magnet ring is shown to be formed, as heretofore, of numerousthin rings of sheetiron held together side by side and each having slotscut through it for the windings to pass through.

The armature may be of the well-known squirrel-cage or of other suitableconstruction.

A are the running-coils, with the ends of the winding carried toterminals A B B are the starting-coils, of more numerous turns andusually of thinner wire to occupy less space and with the ends of thewindings carried to the terminals A O The terminal O is coupled to thecontact O of the switch mechanism. The terminal B is coupled to thecontact B, and this contact is coupled through a resistance R with thecontact 13 The switch-lever D is coupled with one conductor E of asupply-main and the terminal A is coupled to the other conductor E.

For starting the motor the switch-lever D is turned into the positionshown in the drawin g. Current then passes through the resistance R andrunning-coils A at the same time that it also passes through thestarting-coils B. hen the motor has attained suificient speed to allowof its being driven synchronously, the switch-lever is moved over intoits opposite position. Current then passes direct through the coils Awithout passing through the resistance, and no current is passed throughthe starting-coils B.

I claim- An alternating-current motor in which the starting-coils are ofnumerous turns and relatively high self-induction as compared with therunning-coils and in which a resistance is added at starting to thecircuit through the running-coils substantially as described.

IVALTER LANGDON-DAVIES.

Witnesses:

FRED O. HARRIS, WILERED QAEPMAEL.

